Method and apparatus for tuning antennas in a communication device

ABSTRACT

A system that incorporates teachings of the present disclosure may include, for example, a matching network for a communication device having first and second antennas, where the matching network includes a first variable component connectable and a detector. The first variable component can be connectable along a first path between the first antenna and a front end module of the communication device, where the first antenna is configured for transmit and receive operation. The detector can be connectable along a second path between the second antenna and the front end module of the communication device, where the detector obtains an RF voltage associated with the second path, where the second antenna is configured for a diversity receive operation, and where the first variable component is adjusted based on the detected RF voltage to tune the matching network. Additional embodiments are disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.12/941,972 filed on Nov. 8, 2010, the disclosure of which is herebyincorporated by reference in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to communication systems, andmore specifically to a method and apparatus for tuning of antennas.

BACKGROUND

Existing multi-frequency wireless devices (e.g., radios) use an antennastructure that attempts to radiate at optimum efficiency over the entirefrequency range of operation, but can really only do so over a subset ofthe frequencies. Due to size constraints, and aesthetic design reasons,the antenna designer is forced to compromise the performance in some ofthe frequency bands. An example of such a wireless device could be amobile telephone that operates over a range of different frequencies,such as 800 MHz to 2200 MHz. The antenna will not radiate efficiently atall frequencies due to the nature of the design, and the power transferbetween the antenna, the power amplifier, and the receiver in the radiowill vary significantly.

Additionally, an antenna's performance is impacted by its operatingenvironment. For example, multiple use cases exist for radio handsets,which include such conditions as the placement of the handset's antennanext to a user's head, or in the user's pocket or the covering of anantenna with a hand, can significantly impair wireless deviceefficiency. Further, many existing radios use a simple circuit composedof fixed value components that are aimed at improving the power transferfrom power amplifier to antenna, or from the antenna to the receiver,but since the components used are fixed in value there is always acompromise when attempting to cover multiple frequency bands andmultiple use cases.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an illustrative embodiment of a communication device;

FIG. 2 depicts an illustrative embodiment of a portion of a transceiverof the communication device of FIG. 1;

FIGS. 3-4 depict illustrative embodiments of a tunable matching networkof the transceiver of FIG. 2;

FIGS. 5-6 depict illustrative embodiments of a tunable reactive elementof the tunable matching network;

FIG. 7A depicts an illustrative embodiment of a portion of acommunication device;

FIG. 7B depicts a smith chart illustrating output power vs. return loss;

FIG. 8A-8F depict illustrative embodiments of a portion of a multipleantenna communication device;

FIGS. 8G-8Q depict a timing diagram and plots for various tuning methodsusing the communication device of FIG. 8A;

FIG. 9 depicts an illustrative embodiment of a portion of anothermultiple antenna communication device;

FIG. 10 depicts an exemplary method operating in portions of one or moreof the devices of FIGS. 1-9;

FIG. 11 depicts an illustrative embodiment of a look-up table utilizedby one or more of the devices of FIGS. 1-9 and the method of FIG. 10;and

FIG. 12 depicts an exemplary diagrammatic representation of a machine inthe form of a computer system within which a set of instructions, whenexecuted, may cause the machine to perform any one or more of themethodologies disclosed herein.

DETAILED DESCRIPTION

One embodiment of the present disclosure entails a matching network fora communication device having first and second antennas, where thematching network includes a first variable component connectable and adetector. The first variable component can be connectable along a firstpath between the first antenna and a front end module of thecommunication device. The detector can be connectable along a secondpath between the second antenna and the front end module of thecommunication device, where the detector obtains an RF voltageassociated with the second path, and where the first variable componentis adjusted based on the detected RF voltage to tune the matchingnetwork.

In another embodiment, the first antenna can be configured for transmitand receive operation while the second antenna can be configured for adiversity receive operation.

One embodiment of the present disclosure entails a matching network fora communication device. The matching network can include a matchingcircuit and a controller. The matching circuit can be connectable withan antenna, where the matching circuit includes one or more variablereactances with variable reactance values. The controller can beconnectable with the matching circuit, where the controller isconfigured to obtain an RF voltage at an output of the matching circuit.The controller can be configured to determine derivative informationassociated with the RF voltage based on derivatives of the RF voltageand the variable reactance values, where the controller is configured totune the matching circuit using the derivative information.

One embodiment of the present disclosure entails a method of tuning acommunication device having first and second antennas. The method caninclude selectively switching a detector between first and second pathsto obtain operational metrics, where the first path is between the firstantenna and a front end module of the communication device, and thefirst path includes a first variable component. The second path isbetween the second antenna and the front end module of the communicationdevice, and can include a second variable component. The method can alsoinclude independently tuning the first and second antennas by adjustingthe first and second variable components based on the operationalmetrics.

One embodiment of the present disclosure can include a method includingobtaining a first operational metric for a transmitter of acommunication device and determining a range of impedances based on thefirst operational metric, where the range of impedances is associatedwith an acceptable level of performance for the communication device.The method can include obtaining a second operational metric for thetransmitter and determining a target impedance within the range ofimpedances based on the second operational metric. The method can alsoinclude tuning a first impedance matching network based on the targetimpedance, where the first impedance matching network is coupled with afirst antenna of the communication device. The tuning can be based onadjusting a first variable component of the first impedance matchingnetwork.

One embodiment of the present disclosure entails a method of tuning acommunication device, where the method includes obtaining an RF voltageat an output of a tunable matching network of the communication device.The RF voltage can be obtained at a transmission frequency of thecommunication device using a detector, and the tunable matching networkcan have one or more variable capacitors with variable capacitancevalues. The method can further include determining derivativeinformation associated with the RF voltage based on derivatives of theRF voltage and the variable capacitance values, and tuning the tunablematching network using the derivative information.

One embodiment of the present disclosure entails a non-transitorycomputer-readable storage medium with computer instructions to obtainone or more operational metrics for a transceiver of a communicationdevice and calculate a current figure of merit as a function of the oneor more operational metrics. The computer instructions can also comparethe current figure of merit to a target figure of merit and adjust asetting of a variable component of a tunable matching network to a valueexpected to change the current figure of merit relative to the targetfigure of merit. The tunable matching network can be connected with oneof a first antenna or a second antenna of the communication device.

One embodiment of the present disclosure entails a matching network fora communication device, where the matching network includes a firstvariable component connectable along a first path between a firstantenna and a front end module of the communication device, and a secondvariable component connectable along a second path between a secondantenna and the front end module of the communication device. Thematching network can also include a switching element for selectivelyswitching a detector between the first and second paths to obtainoperational metrics, where the first and second antennas can beindependently tuned by adjusting the first and second variablecomponents based on the operational metrics.

FIG. 1 depicts an exemplary embodiment of a communication device 100.The communication device 100 can comprise a wireless transceiver 102(herein having independent transmit and receive sections and having oneor more antennas (two of which are shown in this example)), a userinterface (UI) 104, a power supply 114, and a controller 106 formanaging operations thereof. The wireless transceiver 102 can utilizeshort-range or long-range wireless access technologies such asBluetooth, WiFi, Digital Enhanced Cordless Telecommunications (DECT), orcellular communication technologies, just to mention a few. Cellulartechnologies can include, for example, CDMA-1X, WCDMA, UMTS/HSDPA,GSM/GPRS, TDMA/EDGE, EV/DO, WiMAX, and next generation cellular wirelesscommunication technologies as they arise.

The UI 104 can include a depressible or touch-sensitive keypad 108 witha navigation mechanism such as a roller ball, joystick, mouse, ornavigation disk for manipulating operations of the communication device100. The keypad 108 can be an integral part of a housing assembly of thecommunication device 100 or an independent device operably coupledthereto by a tethered wireline interface (such as a flex cable) or awireless interface supporting for example Bluetooth. The keypad 108 canrepresent a numeric dialing keypad commonly used by phones, and/or aQwerty keypad with alphanumeric keys. The UI 104 can further include adisplay 110 such as monochrome or color LCD (Liquid Crystal Display),OLED (Organic Light Emitting Diode) or other suitable display technologyfor conveying images to an end user of the communication device 100. Inan embodiment where the display 110 is a touch-sensitive display, aportion or all of the keypad 108 can be presented by way of the display.

The power supply 114 can utilize common power management technologies(such as replaceable batteries, supply regulation technologies, andcharging system technologies) for supplying energy to the components ofthe communication device 100 to facilitate portable applications. Thecontroller 106 can utilize computing technologies such as amicroprocessor and/or digital signal processor (DSP) with associatedstorage memory such a Flash, ROM, RAM, SRAM, DRAM or other liketechnologies.

FIG. 2 depicts an illustrative embodiment of a portion of the wirelesstransceiver 102 of the communication device 100 of FIG. 1. In GSMapplications, the transmit and receive portions of the transceiver 102can include common amplifiers 201, 203 coupled to a tunable matchingnetwork 202 and an impedance load 206 by way of a switch 204. The load206 in the present illustration can be an antenna as shown in FIG. 1(herein antenna 206). A transmit signal in the form of a radio frequency(RF) signal (TX) can be directed to the amplifier 201 which amplifiesthe signal and directs the amplified signal to the antenna 206 by way ofthe tunable matching network 202 when switch 204 is enabled for atransmission session. The receive portion of the transceiver 102 canutilize a pre-amplifier 203 which amplifies signals received from theantenna 206 by way of the tunable matching network 202 when switch 204is enabled for a receive session. Other configurations of FIG. 2 arepossible for other types of cellular access technologies such as CDMA.These undisclosed configurations are contemplated by the presentdisclosure.

FIGS. 3-4 depict illustrative embodiments of the tunable matchingnetwork 202 of the transceiver 102 of FIG. 2. In one embodiment, thetunable matching network 202 can comprise a control circuit 302 and atunable reactive element 310. The control circuit 302 can comprise aDC-to-DC converter 304, one or more digital to analog converters (DACs)306 and one or more corresponding buffers 308 to amplify the voltagegenerated by each DAC. The amplified signal can be fed to one or moretunable reactive components 504, 506 and 508 such as shown in FIG. 5,which depicts a possible circuit configuration for the tunable reactiveelement 310. In this illustration, the tunable reactive element 310includes three tunable capacitors 504-508 and an inductor 502 with afixed inductance. Other circuit configurations are possible, and therebycontemplated by the present disclosure.

The tunable capacitors 504-508 can each utilize technology that enablestunability of the capacitance of said component. One embodiment of thetunable capacitors 504-508 can utilize voltage or current tunabledielectric materials such as a composition of barium strontium titanate(BST). An illustration of a BST composition is the Parascan® TunableCapacitor. In another embodiment, the tunable reactive element 310 canutilize semiconductor varactors. Other present or next generationmethods or material compositions that can support a means for a voltageor current tunable reactive element are contemplated by the presentdisclosure.

The DC-to-DC converter 304 can receive a power signal such as 3 Voltsfrom the power supply 114 of the communication device 100 in FIG. 1. TheDC-to-DC converter 304 can use common technology to amplify this powersignal to a higher range (e.g., 30 Volts) such as shown. The controller106 can supply digital signals to each of the DACs 306 by way of acontrol bus of “n” or more wires to individually control the capacitanceof tunable capacitors 504-508, thereby varying the collective reactanceof the tunable matching network 202. The control bus can be implementedwith a two-wire common serial communications technology such as a SerialPeripheral Interface (SPI) bus. With an SPI bus, the controller 106 cansubmit serialized digital signals to configure each DAC in FIG. 3 or theswitches of the tunable reactive element 404 of FIG. 4. The controlcircuit 302 of FIG. 3 can utilize common digital logic to implement theSPI bus and to direct digital signals supplied by the controller 106 tothe DACs.

In another embodiment, the tunable matching network 202 can comprise acontrol circuit 402 in the form of a decoder and a tunable reactiveelement 404 comprising switchable reactive elements such as shown inFIG. 6. In this embodiment, the controller 106 can supply the controlcircuit 402 signals via the SPI bus which can be decoded with commonBoolean or state machine logic to individually enable or disable theswitching elements 602. The switching elements 602 can be implementedwith semiconductor switches or micro-machined switches, such as utilizedin micro-electromechanical systems (MEMS). By independently enabling anddisabling the reactive elements (capacitor or inductor) of FIG. 6 withthe switching elements 602, the collective reactance of the tunablereactive element 404 can be varied.

The tunability of the tunable matching networks 202, 204 provides thecontroller 106 a means to optimize performance parameters of thetransceiver 102 such as, for example, but not limited to, transmitterpower, transmitter efficiency, receiver sensitivity, power consumptionof the communication device, a specific absorption rate (SAR) of energyby a human body, frequency band performance parameters, and so on.

FIG. 7A depicts an exemplary embodiment of a portion of a communicationdevice 700 (such as device 100 in FIG. 1) having a tunable matchingnetwork which can include, or otherwise be coupled with, a number ofcomponents such as a directional coupler, a sensor IC, control circuitryand/or a tuner. The tunable matching network can include various othercomponents in addition to, or in place of, the components shown,including components described above with respect to FIGS. 1-6. Inaddition to the detector 701 coupled to the directional coupler 725,there is shown a detector 702 coupled to the RF line feeding the antenna750. A tunable matching network 775 can be coupled to the antenna 750and a transceiver 780 (or transmitter and/or receiver) for facilitatingcommunication of signals between the communication device 700 andanother device or system. In this exemplary embodiment, the tunablematch can be adjusted using all or a portion of the detectors forfeedback to the tuning algorithm. FIG. 7B depicts a smith chartillustrating output power vs. load impedance for a communication devicewith a tunable network.

Various algorithms can be utilized for tuning of the antenna 750, someof which are disclosed in U.S. Patent Application Publication No.2009/0121963 filed on Nov. 14, 2007 by Greene, the disclosure of whichis hereby incorporated by reference herein. The Greene Applicationdescribes several methods utilizing Figures of Merit, which in thisexemplary embodiment can be determined in whole or in part frommeasurements of the forward and reverse signals present at detector 701.This exemplary embodiment, can also utilize detector 702 to furtherimprove the ability of the tuning system to enable improved performanceof the communication device. One embodiment of the algorithm can utilizethe inputs from detector 701 to establish a maximum return loss or VSWRfor the matching network. This method can establish a range ofimpedances around the targeted impedance. This range of impedances mayestablish an acceptable level of performance. Input from detector 702can then be utilized to allow the algorithm to find an improved or bestimpedance within that acceptable range. For instance, the algorithmcould continue to modify the matching network 775 in order to increasethe RF voltage detected at the antenna feed, while constraining thereturn loss (measured by detector 701) to stay within the target returnloss. In this embodiment, communication device 700 can allow tuning forsource impedances that are not 50 ohms In this example, the lowestinsertion loss can be chosen for the tuning algorithm.

In another embodiment, the tuning algorithm can maintain the return losswhile minimizing the current drain to determine desired tuning values.The tuning algorithm can utilize various parameters for tuning thedevice, including output power of the transmitter, return loss, receivedpower, current drain and/or transmitter linearity.

In another exemplary embodiment, FIG. 8A depicts a portion of acommunication device 800 (such as device 100 in FIG. 1) having tunablematching networks for use with a multiple antenna system. In thisexemplary embodiment, there are two antennas, which are atransmit/receive antenna 805 and a diversity reception antenna 820.However, it should be understood that other numbers, types and/orconfigurations of antennas can be utilized with device 800. Forinstance, the antennas can be spatially diverse, pattern diverse,polarization diverse and/or adaptive array antennas. In one embodiment,the antennas can be part of a MIMO (multiple-input and multiple output)system. The multiple antennas can be utilized for improvingcommunications, such as through switching or selecting techniques,including analyzing noise in the multiple signals and selecting the mostappropriate signal. The multiple antennas can also be used withcombining techniques where the signals can be added together, such asequal gain combining or maximal-ratio combining. Other techniques forutilizing multiple signals from multiple antennas are also contemplatedby the exemplary embodiments, including dynamic systems that can adjustthe particular techniques being utilized, such as selectively applying aswitching technique and a combination technique. The particularposition(s) of the antenna(s) can vary and can be selected based on anumber of factors, including being in close enough proximity to coupleRF energy with each other.

Communication device 800 can include a number of other components suchas tunable matching networks which can include or otherwise be coupledwith a number of components such as directional couplers, sensor ICs,bias control and other control ICs and tunable matching networks. Thetunable matching networks can include various other components inaddition to, or in place of the components shown, including componentsdescribed above with respect to FIGS. 1-7. This example also includes atransceiver 850 of the communication device 800 that includes multiplereceivers and/or transmitters for the multiple antennas 805 and 820 toserve the purpose of diversity reception.

In one embodiment, a first tunable matching network 810 can be coupledat the input to the transmit/receive antenna 805 and a second tunablematching network 825 can be coupled to the input to the diversityreception antenna 820. Both of these matching networks 810 and 825 canbe adjusted (e.g., tuned) to improve performance of the communicationdevice 800 in response to changes in bands, frequencies of operation,physical use cases and/or proximity of the antennas 805 and 820 to theuser or other objects which can affect the impedances presented by theantennas to the Front End Module (FEM) 860 and transceiver 850. In oneembodiment, the feedback line could be removed, such as by using the FEMto route these signals appropriately to perform these measurements(e.g., avoiding filtering out the signals).

Tunable matching network 810 can be adjusted using different methodsand/or components, some of which were disclosed in U.S. PatentApplication Publication No. 2009/0121963. In one embodiment, a detector830 can be coupled to the device 800 so as to detect RF voltage presentat the connection to the diversity reception antenna 820. Received powerlevels at this point may be below −50 dBm. Some detectors, such as adiode detector or a logarithmic amplifier, may not typically be adequateto detect such levels. However, since in this exemplary embodiment, thetwo antennas 805 and 820 are in the same device 800 and in proximity toeach other, they can inherently couple RF energy from one antenna to theother. While the communication device 800 does not require thiscoupling, its presence can be utilized by the exemplary embodiments forthe purposes of tuning the antenna matching networks. In one example,after establishing the tuning state for the diversity match at thetransmit frequency, a predetermined relationship or offset can beapplied to the matching network 825 in order to adjust the match to thereceiver operating frequency.

In one embodiment, the tunable match on the transmit/receive antenna 805can be tuned similar to the technique described above with respect toFIG. 7A but instead of using detector 815, detector 830 can be used tomeasure increases in transmitted RF power coupled to the diversityreception antenna 820. As such, detector 815 (shown in broken lines inFIG. 8A) can be removed from the device 800, thereby reducing the costand complexity. Thus, this example would tune both antennas utilizingonly one detector (e.g., detector 830) coupled with one of the antennas(e.g., the diversity reception antenna 820) and without another detectorcoupled to the other antenna. This example relies upon a fairly constantcoupling coefficient between the two antennas at any particular band,frequency and use case, and for any operation of the algorithm these mayall be considered constant.

Communication device 800 can include other components and configurationsfor determining, or otherwise measuring, parameters to obtain thedesired tuning. Various configurations are illustrated in FIGS. 8B-8F.FIG. 8B illustrates a capacitive coupling configuration between thetunable matching network and the FEM. FIG. 8C illustrates a resistivecoupling between the tunable matching network and the FEM for obtainingthe desired parameters. The FEM 860 in the diversity path of thecommunication device 800 may be highly reflective at the transmissionfrequency. This can create a standing wave and the detector may be at avoltage minimum causing detection to be made more difficult for thecapacitive and resistive couplings shown in FIGS. 8A and 8B. In FIG. 8D,a directional coupler can be utilized to sample only the forward power,which allows for obtaining the desired parameters despite the existenceof any standing wave in the diversity path. FIGS. 8E and 8F utilizedetectors, but sample multiple points along the path to avoid samplingat a voltage minimum.

In another embodiment, after tunable matching network 810 is adjusted bythe algorithm, tunable matching network 825 can also be adjusted. Bymeasuring the coupled transmitted power present at detector 830, thetunable matching network 825 can be adjusted to increase coupledtransmitter power seen at detector 830. In one example, afterestablishing the tuning state for the diversity match at the transmitfrequency, a predetermined relationship or offset can be applied to thematching network 825 in order to adjust the match to the receiveroperating frequency. For instance, the tuning circuits can be adjustedinitially based on transmitter oriented metrics and then a predeterminedrelationship or offset can be applied to attain a desired tuning statefor both transmitter and receiver operation. In another embodiment, theoperational metric can be one or more of transmitter reflection loss,output power of the transmitter, current drain and/or transmitterlinearity.

For example, in a time division multiplexed (TDM) system in which thetransmitter and the receiver operate at different frequencies but onlyoperate in their respective time slots (i.e., transmit time slot andreceive time slot), this can be accomplished by identifying an optimaltuning for the transmitter and then adding an empirically derivedadjustment to the tuning circuits in receive mode. As another example,in a frequency division multiplexed (FDM) system in which thetransmitter and receiver operate simultaneously and at differentfrequencies, this can be accomplished by identifying a target operationfor the transmitter, and then adjusting the tuning circuits first to thetarget value for the transmitter and then adjusting the values toapproach a compromised value proximate to an equal or desired targetvalue for the receiver. In one embodiment, a predetermined relationship,(e.g., an offset, scaling factor, translation or other change ormodification) can be applied to the adjustments of the variablecomponents when switching from the transmit mode to the receive mode.This translation can be a function of the values obtained whileadjusting during the transmit time slot. The translation can then beremoved upon return to the transmitter mode and the adjustment processis resumed. In one embodiment, because any frequency offset between thetransmit signal and the receive signal is known, an adjustment ormodification of the setting of the matching network in the form of atranslation or some other function can be applied to the matchingnetwork during the receive time slot. In another embodiment, theadjustment can be performed in multiple steps if the transmission andreception frequencies are far apart.

In another embodiment, a Figure of Merit can be utilized that not onlyincorporates the transmit metrics, but also incorporates an element toattain a compromise between optimal transmitter and optimal receiveroperation. This can be accomplished by identifying a target operationgoal, such as a desired transmitter and receiver reflection loss andthen identifying an operational setting that is a close compromisebetween the two. This embodiment thus can incorporate not onlytransmitter metrics but also tuning circuit settings or preferences intothe algorithm. The tuning preferences can be empirically identified toensure the desired operation.

In one embodiment where the communication device 800 employs antennadiversity for receive operation but does not employ antenna diversityfor transmit operation, antenna 820 would be receive only. Thetransceiver can transmit on antenna 805 and can receive on both antennas805 and 820. For adaptive closed loop tuning of the tunable matchingnetwork 825 on the diversity antenna, the communication device 800 canobtain a metric indicating the performance of the tunable matchingcircuit at the receive frequency. The metric can be used to tune thematch to adjust the performance at the receive frequency. This can bedone by measuring the level of the received signal using the receiver inthe transceiver IC. This measurement is known as RSSI, received signalstrength indicator. An RSSI measurement can be very noisy and unstabledue to highly variable impairments in the propagation channel, such asfading. These variations can be filtered using averaging. However, theamount of averaging necessary could make such a measurementprohibitively slow and not suitable as feedback for closed loop antennatuning.

In this embodiment, the transmit signal is moderately coupled to thetunable match in the diversity path because the main antenna and thediversity antenna are located on the same communications device. Themain antenna and the diversity antenna may only have 20 dB isolation inmany cases. The transmit signal present at tunable match 825 may be amuch stronger and more stable signal than the receive signal present attunable matching network 825. The transmit signal can be used to makereliable measurements that can be used for closed loop tuning.

The transmit signal can be measured using detector 830. The detector canbe placed between the tunable match and the transceiver. This iseffectively the output of the tunable match. A directional coupler isnot necessary for this measurement in this embodiment, and capacitive orresistive coupling may be used, as long as the detector has sufficientdynamic range. Other components and configurations of the components canalso be utilized for the parameter detection, such as shown in U.S.Patent Publication No. 20090039976 by McKinzie, the disclosure of whichis hereby incorporated by reference.

In this embodiment, maximizing the output voltage of a tunable match canbe the equivalent to minimizing insertion loss, and for a losslessnetwork it can be equivalent to minimizing mismatch loss. An alternativeto using detector 830 is to use the receiver itself (tuned to thetransmit frequency) to measure the transmit signal. These are a fewviable methods for measuring the transmit signal through the diversitytunable match. Other forms of signal detection are contemplated by thepresent disclosure.

A complication with using the transmit signal for tuning can be that itis at a different frequency than the receive signal and the objective ofthe tunable match in the diversity path is to adjust performance at thereceive frequency. In one exemplary method, the tunable matching circuitis adjusted for reception performance based on transmissionmeasurements. In this exemplary method, a tunable match can be optimizedat the transmit frequency using measurements on the transmit signal andthen the matching circuit can be adjusted using a predeterminedrelationship between the transmit settings and the receive settings toprovide the desired performance at the receive frequency.

Referring to FIGS. 8G-8I and applying this same technique to tuning thediversity antenna, there can be two sets of tuning values for thetunable capacitors. This is illustrated in the timing diagram of FIG. 8Gand the plots of FIGS. 8H and 8I, where the exemplary tunable matchingnetwork contains two tunable capacitors. One set of tuning values,designated (C1TX, C2TX), can be applied only during the measurement ofthe transmit signal. The other set of tuning values, designated (C1RX,C2RX), can be applied in between the transmit measurements. In thisembodiment, the Rx tuning values are a function of the Tx tuning values.As the Tx values adaptively change throughout the iterative algorithm,the Rx values will also change, tracking the Tx values with apredetermined relationship. If the figure of merit is set to maximizeVout, the Tx solution can converge at (C1TXopt, C2TXopt), and can beappropriately adjusted using the predetermined relationship to (C1RXopt,C2RXopt) to achieve the desired RX performance.

Each time the tunable match is set to (C1TX, C2TX) in order to perform aTx measurement, the performance at the Rx frequency may be degradedduring the time that (C1TX, C2TX) is applied. It is desirable in thisembodiment to perform the measurement as quickly as possible to minimizethe Rx degradation caused by Tx tuning during the measurement. In oneembodiment, the Tx values can be applied for less than one percent ofthe time while still achieving adequate convergence time.

Referring to FIGS. 8J-8M, another exemplary method for controlling thetuning can be employed, which does not require setting the tunablecapacitors to values optimized for transmission while performing the Txmeasurement. The objective is to operate the tuning matching network atsettings that optimize Rx performance. These settings are at capacitancevalues that are a specific amount away from the Tx optimum in a specificdirection. An algorithm can be utilized that will find this location inthe capacitance plane without first needing to find the Tx optimum. TheTx level can change based on a number of circumstances, such as frompower control commands in the transceiver or from variations in supplyvoltage, temperature, component tolerances, and so forth. In thisembodiment, since only measurement of the output RF voltage of the tuneris being performed, a determination may not be made as to whether thealgorithm is at the Tx optimum or a specific amount away from the Txoptimum because the Tx level is changing. This may prevent the use of analgorithm that simply targets a specific Tx signal level.

A metric that can be useful in determining where the tuning matchingnetwork is operating relative to the Tx optimum is to utilize the slope,or derivative of the Tx level with respect to the value or setting ofthe tunable capacitors. If the RF voltage (Vout) present at the outputof the tunable match at the TX frequency is determined, such as throughuse of a log detector, then the first derivatives are dVout/dC1 anddVout/dC2. These derivatives can be calculated using the finitedifference of two sequential measurements. These slopes will be afunction of the tunable capacitors as shown in FIG. 8J. These slopeswill not be a function of the absolute power level of the Tx signalsince we are using a log detector. If a log detector or its equivalentis not utilized, the logarithm of the Tx voltage can be calculated priorto calculating the slope. By defining a Figure of Merit that includesdVout/dC1 and dVout/dC2, the algorithm can converge to a solution thatis a specific amount away from the Tx optimum in a specific direction,in this case near the Rx optimum. In this embodiment, a log detector isa device having a logarithmic response.

In some cases, specifying the slopes alone will not result in a uniquesolution (i.e., there may be multiple solutions). This is illustrated bythe two intersection points along the contours in FIG. 8K. The algorithmcan resolve this situation by adding a PTC preference to the Figure ofMerit. A tunable match may have many solutions that meet a Tx RL goaland a PTC preference can be included in the Figure of Merit to identifya solution that not only meets the Tx RL goal but also meets an Rxperformance goal. Similarly, a tunable match may have many solutionsthat meet a slope criteria and a PTC preference can be included in theFigure of Merit to identify a solution that not only meets the slopecriteria but also meets an Rx performance goal. FIG. 8L illustrates theresult of using a Figure of Merit that includes dVout/dC1, dVout/dC2,and a PTC preference.

In cases where using dVout alone results in multiple solutions, it isalso possible to use the second derivative to resolve these cases. FIG.8M illustrates use of second derivatives (d²Vout/dC2 dC1), which isdVout/dC2 differentiated with respect to C1. It can be seen thatspecifying dVout/dC2 and d²Vout/dC2 dC1 can identify the correct ordesired Rx solution from the multiple solutions. This exemplary methodcan include determining derivative information (e.g., one or more of afirst derivative, and/or a second derivative, and/or etc.) associatedwith the RF voltage based on derivatives of the RF voltage and thevariable capacitance values, and tuning the tunable matching networkusing the derivative information.

Referring to FIGS. 8N-8Q, another exemplary embodiment can use detector830 of the communication device 800 in the diversity path as feedback toadjust tunable matching network 810 on the main antenna 805. The tunablematching network 810 coupled with the main antenna has both transmit andreceive signals, and can be optimized for Tx performance, Rxperformance, and Duplex performance. For the Tx solution, Vout can bemaximized. For the Rx solution and the Duplex solution, dVout can beincluded in the Figure of Merit. FIG. 8N illustrates Tx and Rx ILcontours and identifies the optimum tuning for Tx, Rx, and Duplexoperation. FIG. 8 o overlays the dVout contours with the optimal tuningsolutions. It can be seen that in this case a PTC preference is requiredto identify the optimal Rx solution but is not required to identify theoptimal duplex solution. FIG. 8P illustrates the closed loop resultusing a Figure of Merit with dVout/dC1 and dVout/dC2. FIG. 8Qillustrates the closed loop result using a Figure of Merit withdVout/dC2 and d²Vout/dC2 dC1.

In one or more exemplary embodiments, the Figure of Merit may beconstructed such that when it equals a certain value, or is minimized ormaximized, the desired tuner settings are achieved. The Figure of Meritmay be used with a number of different optimization algorithms. Forexample, a more exhaustive approach may be used that evaluates theFigure of Merit at every combination of capacitor values. Other suitablealgorithms can also be utilized, including a simplex algorithm, a binarysearch algorithm, and/or a gradient algorithm.

In another embodiment, communication device 800 can tune antennas 805and 820 without using detectors 815 and 830. The tunable matchingnetwork 810 can be adjusted using several different methods, some ofwhich were disclosed in U.S. Patent Application Publication US2009/0121963. After the tunable matching network 810 is adjusted, thetunable matching network 825 can be adjusted. By monitoring the detector801 coupled to the directional coupler 875, the diversity match tuningstate can be determined which adjusts the tunable matching network 825to the transmit frequency. If significant coupling between the twoantennas 805 and 820 is assumed, and by monitoring the return loss ofthe transmit/receive match while adjusting the diversity receptionantenna 820 match during transmitting, the diversity match tuning statecan be determined which tunes the diversity reception antenna 820 to thetransmit frequency. This tuning state can minimize the return loss atthe transmit frequency as measured at the directional coupler 875. Afterfinding this tuning state the tunable matching network 825 can then beadjusted (e.g., offset) appropriately for the receive frequency.

In another exemplary embodiment, FIG. 9 depicts a portion of acommunication device 900 (such as device 100 in FIG. 1) having tunablematching networks for use with a multiple antenna system. Device 900depicts an exemplary embodiment in which the transmit/receive antenna905, the diversity antenna 920 and tunable matching networks 910 and 925are connected to the directional coupler 975 and front end module 960through a switching element 930, which enables the two antennas 905 and920 to be switched between the two corresponding connections to the FEM960. In one embodiment, the switching element 930 can be a double-poledouble-throw RF switch, although other switching components andtechniques are also contemplated. This exemplary embodiment can allowthe two antennas 905 and 920 to be tuned independently using thetransmitted signal present at the detector 901 coupled to thedirectional coupler 975. Various tuning methods or algorithms could beused to tune each antenna, such as described above and/or in U.S. PatentApplication Publication US 2009/0121963. When an antenna is connected tothe diversity receiver path, the tuning network 925 can be offsetappropriately to adjust it to the receive frequency of operation. Thetransmit/receive antenna 905 can be tuned for various communicationprotocols or techniques, including TDD and/or FDD operation.

In one embodiment, tuning algorithms can be modified with the additionalstep of switching the paths between transmit/receive and diversityreception in order to update the tuning of the two antennas 905 and 920on a frequent basis. Since the diversity reception antenna 920 may notbe as well suited for transmission as the transmit/receive antenna 905,the amount of time the algorithm spends with the transmitter connectedto the diversity receive antenna 920 may be reduced or otherwise kept toa minimum, but enough to provide for tuning feedback to correct forenvironmental detuning.

In another embodiment, the switch 930 can drive the diversity antenna930 directly so that the system effectively is providing antennaswitching diversity on the transmit path. For example, relativereception levels on the two paths can be monitored in order to selectwhich antenna is used to transmit. For instance, averaging or otheranalysis techniques can be utilized, which would then give an indicationof which antenna is experiencing more interference (e.g., beingsmothered) and is experiencing the higher dissipative loss, such as dueto nearby body effects. Continuing with this example, step phase changescould be accounted for by timing the switching to periods when thetransmitter is inactive for an extended time and the limitation on phasechange is relaxed or non-existent. This example could be utilized for avariety of situations, including at times other than when there arerapid changes in signal due to fading. The present disclosure alsocontemplates performing calibration of transmit and receive power levelswhen performing the antenna switching methodology described above.

FIG. 10 depicts an exemplary method 1000 operating in portions of one ormore of the devices of FIGS. 1-9. Method 1000 can be utilized withcommunication devices of various configurations, including multipleantenna devices. Method 1000 can begin with step 1002 by detecting firstparameters associated with transmitting of the communication device,such as using a directional coupler connected between a front end moduleand a matching network of a transmit/receive antenna. The directionalcoupler can take measurements based on the forward and reverse signalsand in step 1004 a maximum return loss or voltage standing wave ratio(VSWR) can be determined from the first parameters.

Utilizing this return loss or VSWR information, a range of impedancesfor an acceptable level of performance of the communication device canbe established in step 1006. Method 1000 can next determine a second setof parameters that can be utilized for tuning For instance, in step1008, a detector positioned at the input of the transmit/receive antennacan detect the second parameters, such as changes or increases intransmitted RF power. In another example in step 1010, the secondparameters can be detected by a detector positioned at the input of thediversity reception antenna based on inherent coupling of RF energybetween the antennas when they are positioned in proximity to each otherin a device. In this example, the communication device can operatewithout a detector positioned at the input to the transmit/receiveantenna, which has the advantage of cost savings. This example, measuresincreases in transmitted RF power coupled to the diversity receptionantenna.

In step 1012, a target impedance within the range of impedances can bedetermined using the second parameters. In step 1014, the matchingnetwork for the transmit/receive antenna can be tuned based on thetarget impedance. For example, method 1000 can continue to modify thematching network of the transmit/receive antenna to increase thedetected RF voltage while constraining the return loss within a desiredrange. In step 1016, an offset can be applied for tuning of the antennasin the receive mode. The offset can be based on the techniques describedabove, such as based on a translation where the frequency offset isknown for the receive mode.

In one embodiment, the tuning of the matching network(s) can beperformed in combination with look-up tables such as shown in FIG. 11.For instance, one or more desirable performance characteristics of acommunication device 100 can be defined in the form of Figures of Merits(FOMs), the communication device can be adapted to find a range oftuning states that achieve the desired FOMs by sweeping a mathematicalmodel in fine increments to find global optimal performance with respectto the desired FOMs. In one embodiment, look-up table 1100 can beindexed (e.g., by the controller 106 of the communication device 100 ofFIG. 1) during operation according to band, and use case.

From the foregoing descriptions, it would be evident to an artisan withordinary skill in the art that the aforementioned embodiments can bemodified, reduced, or enhanced without departing from the scope andspirit of the claims described below. For example, detector 830 mayinclude a directional coupler for the diversity antenna to compensatefor out-of-band impedance of the Rx filter that may create a very highstanding wave on the feed line and put voltage nulls at unpredictableplaces on the line (including at the base of the antenna).

Other suitable modifications can be applied to the present disclosure.Accordingly, the reader is directed to the claims for a fullerunderstanding of the breadth and scope of the present disclosure.

FIG. 12 depicts an exemplary diagrammatic representation of a machine inthe form of a computer system 1200 within which a set of instructions,when executed, may cause the machine to perform any one or more of themethodologies discussed above. In some embodiments, the machine operatesas a standalone device. In some embodiments, the machine may beconnected (e.g., using a network) to other machines. In a networkeddeployment, the machine may operate in the capacity of a server or aclient user machine in server-client user network environment, or as apeer machine in a peer-to-peer (or distributed) network environment.

The machine may comprise a server computer, a client user computer, apersonal computer (PC), a tablet PC, a laptop computer, a desktopcomputer, a control system, a network router, switch or bridge, or anymachine capable of executing a set of instructions (sequential orotherwise) that specify actions to be taken by that machine. It will beunderstood that a device of the present disclosure includes broadly anyelectronic device that provides voice, video or data communication.Further, while a single machine is illustrated, the term “machine” shallalso be taken to include any collection of machines that individually orjointly execute a set (or multiple sets) of instructions to perform anyone or more of the methodologies discussed herein.

The computer system 1200 may include a processor 1202 (e.g., a centralprocessing unit (CPU), a graphics processing unit (GPU, or both), a mainmemory 1204 and a static memory 1206, which communicate with each othervia a bus 1208. The computer system 1200 may further include a videodisplay unit 1210 (e.g., a liquid crystal display (LCD), a flat panel, asolid state display, or a cathode ray tube (CRT)). The computer system1200 may include an input device 1212 (e.g., a keyboard), a cursorcontrol device 1214 (e.g., a mouse), a disk drive unit 1216, a signalgeneration device 1218 (e.g., a speaker or remote control) and a networkinterface device 1220.

The disk drive unit 1216 may include a machine-readable medium 1222 onwhich is stored one or more sets of instructions (e.g., software 1224)embodying any one or more of the methodologies or functions describedherein, including those methods illustrated above. The instructions 1224may also reside, completely or at least partially, within the mainmemory 1204, the static memory 1206, and/or within the processor 1202during execution thereof by the computer system 1200. The main memory1204 and the processor 1202 also may constitute machine-readable media.

Dedicated hardware implementations including, but not limited to,application specific integrated circuits, programmable logic arrays andother hardware devices can likewise be constructed to implement themethods described herein. Applications that may include the apparatusand systems of various embodiments broadly include a variety ofelectronic and computer systems. Some embodiments implement functions intwo or more specific interconnected hardware modules or devices withrelated control and data signals communicated between and through themodules, or as portions of an application-specific integrated circuit.Thus, the example system is applicable to software, firmware, andhardware implementations.

In accordance with various embodiments of the present disclosure, themethods described herein are intended for operation as software programsrunning on a computer processor. Furthermore, software implementationscan include, but not limited to, distributed processing orcomponent/object distributed processing, parallel processing, or virtualmachine processing can also be constructed to implement the methodsdescribed herein.

The present disclosure contemplates a machine readable medium containinginstructions 1224, or that which receives and executes instructions 1224from a propagated signal so that a device connected to a networkenvironment 1226 can send or receive voice, video or data, and tocommunicate over the network 1226 using the instructions 1224. Theinstructions 1224 may further be transmitted or received over a network1226 via the network interface device 1220.

While the machine-readable medium 1222 is shown in an example embodimentto be a single medium, the term “machine-readable medium” should betaken to include a single medium or multiple media (e.g., a centralizedor distributed database, and/or associated caches and servers) thatstore the one or more sets of instructions. The term “machine-readablemedium” shall also be taken to include any medium that is capable ofstoring, encoding or carrying a set of instructions for execution by themachine and that cause the machine to perform any one or more of themethodologies of the present disclosure.

The term “machine-readable medium” shall accordingly be taken toinclude, but not be limited to: solid-state memories such as a memorycard or other package that houses one or more read-only (non-volatile)memories, random access memories, or other re-writable (volatile)memories; magneto-optical or optical medium such as a disk or tape;and/or a digital file attachment to e-mail or other self-containedinformation archive or set of archives is considered a distributionmedium equivalent to a tangible storage medium. Accordingly, thedisclosure is considered to include any one or more of amachine-readable medium or a distribution medium, as listed herein andincluding art-recognized equivalents and successor media, in which thesoftware implementations herein are stored.

Although the present specification describes components and functionsimplemented in the embodiments with reference to particular standardsand protocols, the disclosure is not limited to such standards andprotocols. Each of the standards for Internet and other packet switchednetwork transmission (e.g., TCP/IP, UDP/IP, HTML, HTTP) representexamples of the state of the art. Such standards are periodicallysuperseded by faster or more efficient equivalents having essentiallythe same functions. Accordingly, replacement standards and protocolshaving the same functions are considered equivalents.

The illustrations of embodiments described herein are intended toprovide a general understanding of the structure of various embodiments,and they are not intended to serve as a complete description of all theelements and features of apparatus and systems that might make use ofthe structures described herein. Many other embodiments will be apparentto those of skill in the art upon reviewing the above description. Otherembodiments may be utilized and derived therefrom, such that structuraland logical substitutions and changes may be made without departing fromthe scope of this disclosure. Figures are also merely representationaland may not be drawn to scale. Certain proportions thereof may beexaggerated, while others may be minimized. Accordingly, thespecification and drawings are to be regarded in an illustrative ratherthan a restrictive sense.

Such embodiments of the inventive subject matter may be referred toherein, individually and/or collectively, by the term “invention” merelyfor convenience and without intending to voluntarily limit the scope ofthis application to any single invention or inventive concept if morethan one is in fact disclosed. Thus, although specific embodiments havebeen illustrated and described herein, it should be appreciated that anyarrangement calculated to achieve the same purpose may be substitutedfor the specific embodiments shown. This disclosure is intended to coverany and all adaptations or variations of various embodiments.Combinations of the above embodiments, and other embodiments notspecifically described herein, will be apparent to those of skill in theart upon reviewing the above description.

The Abstract of the Disclosure is provided with the understanding thatit will not be used to interpret or limit the scope or meaning of theclaims. In addition, in the foregoing Detailed Description, it can beseen that various features are grouped together in a single embodimentfor the purpose of streamlining the disclosure. This method ofdisclosure is not to be interpreted as reflecting an intention that theclaimed embodiments require more features than are expressly recited ineach claim. Rather, as the following claims reflect, inventive subjectmatter lies in less than all features of a single disclosed embodiment.Thus the following claims are hereby incorporated into the DetailedDescription, with each claim standing on its own as a separately claimedsubject matter.

What is claimed is:
 1. A matching network for a communication devicehaving first and second antennas, the matching network comprising: afirst variable component connectable along a first path between thefirst antenna and a front end module of the communication device; and adetector connectable along a second path between the second antenna andthe front end module of the communication device, wherein the detectorobtains an RF voltage associated with the second path, and wherein thefirst variable component is adjusted based on derivative informationassociated with the detected RF voltage to tune the matching network,wherein the derivative information is determined by calculating a finitedifference of two sequential measurements associated with reactancesettings for the matching network.
 2. The matching network of claim 1,wherein the first antenna is configured for transmit and receiveoperation, and wherein the second antenna is configured for a diversityreceive operation.
 3. The matching network of claim 1, comprising asecond variable component connectable along the second path between thesecond antenna and the front end module of the communication device,wherein the RF voltage is obtained from an output of the second variablecomponent.
 4. The matching network of claim 1, wherein the detector isconnectable along the second path using a capacitive coupling.
 5. Thematching network of claim 4, wherein the capacitive coupling comprises aplurality of capacitors to sample power at multiple points along thesecond path.
 6. The matching network of claim 1, wherein the detector isconnectable along the second path using a resistive coupling.
 7. Thematching network of claim 1, wherein the detector is connectable alongthe second path using a directional coupler.
 8. The matching network ofclaim 1, wherein the tuning of the matching network is performed for thetransmit operation.
 9. The matching network of claim 1, wherein thetuning of the matching network is performed for duplex operation of thecommunication device using the derivative information associated withthe detected RF voltage.
 10. The matching network of claim 1, whereinthe tuning of the matching network is performed for the receiveoperation using the derivative information associated with the detectedRF voltage.
 11. A method of operating a handset having a transmitter andfirst and second antennas, the method comprising: setting a firsttunable capacitor to a first value; setting a second tunable capacitorto a second value; transmitting power from the first antenna; measuringa first response at the second antenna; setting the first tunablecapacitor to a third value; measuring a second response at the secondantenna; calculating a finite difference with respect to the firsttunable capacitor based on the first and second responses; calculating afigure of merit that includes the finite difference; and tuning amatching network based on the figure of merit.
 12. The method of claim11, wherein the matching network is coupled to the first antenna. 13.The method of claim 11, wherein the matching network is coupled to thesecond antenna.
 14. The method of claim 11, comprising: setting thesecond tunable capacitor to a fourth value; measuring a third responseat the second antenna; calculating another finite difference withrespect to the second tunable capacitor based on the third response; andcalculating another figure of merit that includes the finite differencewith respect to the first tunable capacitor and the other finitedifference with respect to the second tunable capacitor.
 15. The methodof claim 11, wherein the handset operates in a frequency divisionmultiplex mode.
 16. The method of claim 11, comprising calculatinganother figure of merit that includes a tuning state of the first andsecond tunable capacitors.
 17. The method of claim 11, comprising:tuning the matching network to a compromise between an optimal transmitperformance and an optimal receive performance.
 18. A communicationdevice comprising: first and second antennas; a transmitter; a matchingnetwork coupled with the transmitter; and a controller coupled with thematching network, wherein the controller performs operations comprising:setting a first tunable capacitor to a first value; setting a secondtunable capacitor to a second value; transmitting power from the firstantenna; measuring a first response at the second antenna; setting thefirst tunable capacitor to a third value; measuring a second response atthe second antenna; calculating a finite difference with respect to thefirst tunable capacitor based on the first and second responses;calculating a figure of merit that includes the finite difference; andtuning the matching network based on the figure of merit.